1. Field of the Invention
The invention relates to semiconductor devices and more specifically to glass encapsulated semiconductor diodes and to a method of fusing glass to a body of semiconductor material to form an encapsulation providing passivation, a hermetic seal and environmental protection for a PN junction within the body of semiconductor material.
2. Description of the Prior Art
Prior art semiconductor diodes using glass fused directly to the semiconductor portion of the diode as the sole means of protecting the PN junction from the environment have been limited to relatively low current diodes. An example of such a diode is type UT4005 manufactured and sold by the Unitrode Corporation. It is also known in the prior art to encapsulate semiconductor devices in thermosetting resinous insulating material. Examples of such hermetically sealed diodes using resinous material are disclosed in Pat. Nos. 3,475,662, 3,476,987 and 3,476,988 as well as 3,486,084. Thin glass protective layers are also available in the prior art to passivate large prior art semiconductor devices. Glass forming these layers was typically applied to the body of semiconductor as a slurry and the device and the powdered glass were heated to fuse the glass and form a protective glass layer. Glass layers formed using this technique were limited to thicknesses in the order of 20 to 30 microns. These thin layers are not sufficient to provide complete environmental protection for PN junctions and other circuit elements within the body of semiconductor material.